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Function

The cardiovascular system circulate blood throughout the body, bringing oxygen and nutrients to muscles and organs, and then returning with wastes in to the heart, cleaning takes place in lungs, to be pumped again. Any opposition in the flow of blood and the working heart can cause damage to an organ, including the heart. The system of channels through which the blood flows is called the circulatory system, and includes the heart, lungs, and blood vessels. Arteries, arterioles (small arteries), and capillaries (tiny blood vessels) carry blood from the heart to the body parts. Veins and venues (small veins) return the blood from the body parts to the heart.

The heart is a muscle about the size of a person's fist in the middle of the chest, tilted toward the left side. The heart beat is an expansion and contraction of the muscle as it pumps. Each day the heart beats about 100,000 times and pumps about 2,000 gallons of blood. It is made up of four chambers: two atria (right and left) and two ventricles (right and left). The atria are the upper chambers that receive the blood from body parts. The lower chambers, the ventricles, are thick-walled chambers made of muscle so they can pump the blood out of the heart. Four valves connecting the chambers, two valves in between artery and ventricle are bicuspid and tricuspid valves and major arteries help pump and carry the blood.

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Strucure

In the human body, the heart is situated in the middle of the thorax with the largest part of the heart slightly offset to the left underneath the sternum. The heart is usually felt to be on the left side because the left heart (left ventricle) is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies more of the left hemi thorax. The heart is covered by the coronary circulation and enclosed by a sac known as the pericardium and it is surrounded by the lungs. The pericardium comprises two parts: the fibrous pericardium, made of dense fibrous connective tissue; and a double membrane structure (parietal and visceral pericardium) containing a serous fluid to reduce friction during heart contractions. The heart is located in the mediastinum, the central sub-division of the thoracic cavity. The mediastinum also contains other structures, such as the esophagus and trachea, and is flanked on either side by the right and left pulmonary cavities, which house the lungs.

The apex is the blunt point situated in an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted. It is located posterior to the 5th intercostals space just medial of the left mid- clavicular line. In normal adults, the mass of the heart is 250-350 g (9-12 oz), or about twice the size of a clenched fist (it is about the size of a clenched fist in children), but extremely diseased hearts can be up to 1000 g (2 lb) in mass due to hypertrophy. It consists of four chambers, the two upper atria and the two lower ventricles.
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